In-ground storage arrangement for liquefied gases

ABSTRACT

A large-scale in-ground storage facility for liquefied gas at cryogenic temperatures consists of an open cavity in the ground covered by an impervious roof sealed at its periphery to a ringbeam extending around the rim of the cavity, which is also sealed to the upper rim of the wall of the cavity. The ring-beam rests on a support structure which extends around the mouth of the cavity, and the ring-beam is mounted on the support structure by thermal expansion means which permit limited relative movement between the ring-beam and its support structure to accommodate thermal expansion and contraction.

0 United States Patent 1151 3,662,558 Jackson May 16, 1972 154] IN-GROUND STORAGE 3,287,914 1 1/1966 Faulconer et al ..6l/0.5 ARRANGEMENT FOR LIQUEFIED 3,292,377 l2/l966 Sanger ..61/0.s SES 3,344,607 l0/l967 Vignovich ..6l/0.5 3,355,892 12/1967 Hamilton et al. ..6l/0.5 [7 Inventor: Robert Jackson, Homchurch, England 3,379,012 4/1968 Jackson ..61 0.5 Assignee: Conch International M Nassau, Jackson Bahamas Primary \'aminer-Meyer Perlin Flledi p 1970 Assistant Examiner-Ronald C. Capossela [21] APPLNO: 76,045 Anorney-Max L. Libmun [57] ABSTRACT [30] Foreign Application Priority Data A large-scale in-ground storage facility for liquefied gas at Nov. 3, 1969 Great Bmam ..53,755/69 cryogenic temperatures consists f an open cavily in the ground covered by an impervious roof sealed at its periphery [52] U.S. Cl ..61/0.5, 62/45 to a ring beam extending around the rim of the cavity which is [51 1 llt. also sealed to the pp rim ofthe n ofthe cavity The g [58] Field of Search ..62/45, 61/05, 220/18 beam rests on a support Structure whihh extends around the f ed 1 mouth of the cavity, and the ring-beam is mounted on the sup- [56] Re erences port structure by thermal expansion means which permit UNITED STATES PATENTS limited relative movement between the ring-beam and its support structure to accommodate thermal expansion and con- 3,l59,006 12/1964 Sliepcevich ..62/45 traction 3,175,370 3/1965 Schlumberger, ..62/45 3,241,274 3/ l 966 Proctor et al. ..62/45 X 10 Claims, 3 Drawing Figures a ll A II 2 5 2 5 24- 1 i i 21 i '19 fifii 6 u 0 v I .V" V. 9 Z Q 2 \4 2s 3s -2,

PKTENTEDM 16 I972 SHEET 1 OF 3 Inventor Roberl' G. JflCKSOH W/lzw Attorney P'A'TENTEDMM 15 I972 SHEET 2- OF 3 Inomlor A r G. Jackson y -1- Mitorney IN-GROUND STORAGE ARRANGEMENT FOR LIQUEFIED GASES This invention relates to in-ground storage arrangements for liquefied gas, i.e. a storage arrangement in which the liquefied gas is contained in a cavity in the surface of the earth which has been adapted for this purpose.

In this specification, the expression "liquefied gas means liquid which boils at atmospheric pressure at a temperature below the ambient temperature, for example liquefied natural gas or methane and liquefied petroleum gases such as ethane, propane, butane, ethylene and propylene.

ln U.S. Pat. No. 3,175,370 an in-ground storage arrangement is described in which a pressure-tight roof structure is provided by an impervious sheet which extends from the roof to the ground where it is sealed in a slot with frozen liquid.

Outside this sheet a separate support structure is provided for the roof comprising plates supported by freeze pipes in turn supporting lined wooden blocks, the roof being held down against these blocks. With thisstructure it would be extremely difficult to obtain pressure-tight conditions; in particular, it would be very time consuming and involved to achieve the pressure-tight connection between the sheet and the roof because it would be necessary to shape and seal parts of the sheet around the support framework for the roof. Also, should the actual roof layer not be connected to its supporting framework to reduce the possibility of stresses being set up as a result of differential thermal movement of these parts it would be even more difficult to connect the sheet to the roof layer since because pressure conditions can exist in the roof space, the sheet would be required to permit movement of the roof layer away from its support framework.

The present invention provides an alternative roof structure which overcomes this difficulty.

According to this invention in an in-ground storage arrangement for liquefied gas of the kind comprising an open cavity in the ground covered by a roof supported on a support structure extending around the mouth of the cavity, and means for sealing the roof to provide a pressure-tight space above the cavity the roof is secured in a pressure-tight manner around its periphery to a ring beam, the ring beam is mounted on the support structure in such a way that it can move'horizontally relative to said support structure, and an impervious sheet is extended between the ring-beam to a part associated with the cavity, the roof, ring-beam and impervious sheet between them providing the pressure-tight space above the cavity.

A tank may be located in the cavity, in which case a layer of thermal insulation may be provided between said tank and the cavity.

The tank and the impervious sheet will be made of a material which is ductile at the operating temperature. A suitable material will have a ratio of ultimate tensile strain to thermal strain over the temperature range to which it may be subjected greater than one. By ultimate tensile strain is meant the elongation which the material undergoes before it fails under the effect of a tensile load. By thermal strain is meant the elongation to which the material is subjected if it is restrained from contracting as it cools from ambient temperature to its operating temperature. Since the material cannot be allowed to fail, which could occur at stress concentrations if the ratio was one, it is preferable that the ratio should be greater than five. Examples of suitable materials are stainless steels, 9 percent nickel steel, INVAR (Registered Trademark), aluminum and certain aluminum alloys.

Conveniently an insulated ceiling structure may be suspended across the mouth of the tank.

The tank may be of the membrane type of self-supporting type and the impervious sheet may extend between the ring and the tank; where the tank is of the membrane type the impervious sheet may be in the form of an extension of its mouth.

The support structure may comprise a number of box sections supported above the earths surface on the upper ends of freeze pipes which extend from holes in the ground spaced around and from the mouth of the cavity.

Vertical beams may be provided within the cavity adjacent the side wall thereof for supporting and locating a membrane tank in the cavity; these beams may extend from a point below the bottom wall of the cavity and may be attached at their upper ends to the roof structure.

In order that the invention may be readily understood two embodiments of an in-ground storage arrangement constructed in accordance with the invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a fragmentary sectional elevation of the first embodiment;

FIG. 2 is a fragmentary sectional elevation of the second embodiment; and

FIG. 3 is a sectional view taken'on line 3--3 of FIG. 2.

Referring to FIG. 1 of the drawings, in the first embodiment a multiplicity-of substantially vertical holes are excavated in a circle around the area of the surface of the earth chosen for the cavity 1 and freeze pipes 4 are located in these holes. The earth is then frozen by the pipes 4 and the cavity 1 excavated. In this embodiment the holes 3 are so spaced around the mouth of the cavity 1 as to provide a number of pairs of freeze pipes 4, each pair comprising an outer and inner pipe lying on a common radial line extending from the center of the cavity 1. The upper ends of each pair of freeze pipes 4 extend above ground level and support a box section 5, and the inner end of this box section is spaced radially from the mouth of the cavity 1. The box sections 5 between them support a ring-beam in the form of a tubular casing 6 which provides an angled wall portion 7 constituting the periphery for the roof 8. The roof 8 is in the form of a domed metal sheet 9 which is welded at its periphery to the wall 7 of the casing 6, the sheet 9 being supported on though preferably not connected to a framework 11. The roof framework 11 is tensioned by tumbuckles 12 which extend between said framework and anchoring members l3 spaced around and secured to the tubular casing 6.

The inner end of each box section 5 is strengthened by an I- section beam 14 which extends vertically into the ground and each of these beams is connected to an adjacent freeze pipe 4, via one or more bracing struts 15. The surface of the earth around the mouth of the cavity 1 is provided with layers of insulation 16 and the cavity itself is lined with insulation 17. A membrane type tank 18 is supported within the insulation lining 17 and the mouth of this tank is extended towards the roof. The tank extension comprises a substantially horizontal annular portion 19 which is supported on the insulation layers 16, a substantially vertical cylindrical portion 21 which is supported against the inner faces of the beams 14 and the inner ends of the box sections 5, and a further substantially horizontal annular portion '22 which is attached to a flange 23 attached to the bottom of the tubular casing 6. The tank extension portions 19, 21, 22 and the roof sheet 9 thus provide a pressure-tight roof space. The flange 23 is provided with radial slots 23a through which bolts 23b pass for attachment to the box sections 5. The slots permit the tubular casing 6 to slide radially with respect to the box sections 5 to cater for any dimensional changes of said tubular casing due to ambient temperature variations and/or should any abnormal pressures build up within the roof space. Further beams 24 are provided which are spaced around the cavity 1 adjacent the side wall thereof and extend vertically from below the bottom of the cavity and are attached at their upper ends to the framework 11 of the roof structure; each of these beams 24 may be a single beam, or may be in two vertically aligned sections which are suitably secured to either side of the portion 19 of the membrane tank 18. The spaces 25 left between the beams 24 and the cavity wall, due to irregularity of this wall, may be packed with, for example, wet sand, which is subsequently frozen. The beams 24 act as strengthening members for the roof structure 8 and at the same time may conveniently be used to support the membrane tank 18 and its insulation 17, for example, as described in my co-pending US. Pat. application Ser. No. 76,138, filed Sept. 28, 1970. A ceiling structure 26 is level that the upper surface of the insulation layers 27 is level with the horizontal annular portion 19 of the membrane tank extension. The ceiling structure and suspension arrangement may, for example, be as described in my co-pending US. Pat. application Ser. No. 71,91 l, filed Sept. 14, 1970. As described in the said co-pending Patent application a gap 28 may be left between the mouth of the membrane tank 18 and the ceiling structure 26, the gap being covered by a porous material covering 29, for example cotton, which allows for boil-ofl gas accumulated in the membrane tank to pass through to the roof space above the ceiling structure. If desired, the space below the box sections 5 may be filled with a suitable insulating material.

It will'be appreciated that the wall of the cavity 1 may be faced with a concrete layer, in which case the beams 24 can conveniently be set into this layer.

It is also possible that a vapor seal, in the event that the ground is frozen to the surface, may be made by extending the substantially vertical cylindrical portion 21 into a trench excavated into the ground surface which is subsequently filled with sand wetted with a fluid which will freeze at operating temperature. In this case, of course, the portion 21 will not form part of an extension to the tank 18, but will be a separate part. With such an arrangement, the annular portion 19 may be dispensed with and in its place, the tank may extend above the level of the insulation layers 16 to guard against the tank' being overfilled and hence spilling liquefied gas over onto the ground surface around the mouth of the cavity 1.

lt is also possible that only one freeze pipe may be used or that the box section 5 may be attached to a concrete support or piles, especially in the case where the ground is not frozen to the surface.

Referring now to FIG. 2, the second embodiment is in many respects similar to the first embodiment and like parts have been given the same reference numerals with primes added. In this embodiment the cavity 1' which may be excavated after pre-freezing the surrounding ground with freeze pipes is lined with a concrete layer 30 and this layer is widened around the mouth of the cavity for added strength. As in the first embodiment box sections 5' are spaced around the mouth of the cavity 1' but instead of being supported by freeze pipes they are supported on pillars 31 which are rigidly attached to the top surface of the concrete layer 30 via a flange 32 and anchoring members 33 set into said concrete layer. Again, as in the first embodiment, the ring beam is in the form of a tubular casing 6' which in this instance is of a modified form and provides an angle section wall portion 7 constituting the periphery for the roof 8'. The anchoring members 13' for the roof framework 11' are carried on the inner face of the tubular casing 6' via angle brackets 34. A membrane tank 18' is supported within the concrete faced cavity 1 by vertical members 24' spaced around the cavity and each member is anchored at spaced positions, e.g. as shown at 35 to the face of the concrete layer 30; in this embodiment the members 24' do not extend up to the roof structure but stop short just above the level of the upper surface of the concrete layer 30. The space between the membrane tank 18' and the face of the concrete layer is filled with suitable thermal insulating material 180 (see FIG. 3) which will withstand the hydrostatic force of the liquefied gas. The wall of the membrane tank 18 is provided with spaced vertical corrugations 36 as shown in FIG. 3, preferably at the position of each member 24 to cater for any circumferential dimensional changes in the wall of the tank as a result of it being subjected to significant temperature variations in use.

As with the first embodiment, the membrane tank 18 is extended to the tubular casing 6 and in this instance the extension comprises a membrane sheet 37 provided with two horizontally extending corrugations 38 which cater for any dimensional changes occurring over the height of said membrane tank. In addition a cylindrical wall 39 is provided suspended across the mouth of the membrane tank at such a between the concrete layer 30 and the tubular casing 6' and fiberglass. As with the first embodiment a ceiling structure 26' is suspended across the mouth of the membrane tank 18' and is provided with insulation layers 27; further insulations layers 16 are provided across the upper surface of the concrete layer 30 and the surrounding ground. The partially open upper ends of the expansion joints 36 of tank 18' are sealed by suitable cover strips 38, since these are above the insulated roof and so are not required to expand significantly because of the thermal protection afforded by the ceiling structure;

I claim:

1. a. A large-scale in-ground storage tank for liquefied gas, of the kind comprising an open cavity in the ground covered by an impervious roof 8,

b. a support structure extending around the mouth of the tank for supporting said roof 3, 4,

c. means for sealing said roof to provide a pressure-tight space above the tank, said sealing means comprising:

d. a ring-beam 6 extending around the periphery of said roof,

e. pressure-tight means 7 sealing said ring-beam to said roof,

f. an impervious sheet 19, 21, 22 extending continuously between said ring-beam and the upper wall of the tank,

g. expansion means between said ring-beam and said supj. and a lining of thermal insulation between saidmembrane sheet and the wall of the cavity.

5. The invention according to claim 1,

k. wherein the cavity wall is faced with a layer of concrete.

6. The invention according to claim 5,

i. wherein the support structure comprises a number of box sections 5 supported above the ground surface on the upper ends of pillars which are rigidly anchored to the upper surface of said layer of concrete.

7. The invention according to claim 1,

h. including vertical beams within said cavity adjacent the side wall thereof, said beams extending from i a point below the bottom of the cavity and supporting and locating the membrane sheet lining the cavity.

8. The invention according to claim 7, V

i. wherein the vertical beams extend to and are attached at their ends to the roof structure.

9. The invention according to claim 3,

j. wherein the inner face of said ring-beam 6 is of a greater diameter than the cavity 1 k. and is supported above the ground level by said support structure 3, 4

l. and said impervious sheet comprises a substantially horizontal annular portion 19 extending radially outward from the mouth of the cavity,

m. and a substantially vertical cylindrical portion 21 extending from the outer periphery of said annular portion to said ring-beam.

10. The invention according to claim 9 n. wherein the support structure comprises a box section 5 supported above the ground surface on the upper ends of freeze pipes which extend upwardly from the ground and are spaced around the mouth of the cavity.

i l I! t 

1. A. A large-scale in-ground storage tank for liquefied gas, of the kind comprising an open cavity in the ground covered by an impervious roof 8, b. a support structure extending around the mouth of the tank for supporting said roof 3, 4, c. means for sealing said roof to provide a pressure-tight space above the tank, said sealing means comprising: d. a ring-beam 6 extending around the periphery of said roof, e. pressure-tight means 7 sealing said ring-beam to said roof, f. an impervious sheet 19, 21, 22 extending continuously between said ring-beam and the upper wall of the tank, g. expansion means between said ring-beam and said support structure to permit limited relative movement between them.
 2. The invention according to claim 1, h. wherein said expansion means mount and retain said ring-beam on said support structure and comprise bolt means passing through radial slot means to permit relative expansion and contraction in the direction of the slots.
 3. The invention according to claim 2, i. said tank comprising an impervious membrane sheet lining the cavity.
 4. The invention according to claim 3, j. and a lining of thermal insulation between said membrane sheet and the wall of the cavity.
 5. The invention according to claim 1, k. wherein the cavity wall is faced with a layer of concrete.
 6. The invention according to claim 5, i. wherein the support structure comprises a number of box sections 5 supported above the ground surface on the upper ends of pillars which are rigidly anchored to the upper surface of said layer of concrete.
 7. The invention according to claim 1, h. including vertical beams within said cavity adjacent the side wall thereof, said beams extending from a point below the bottom of the cavity and supporting and locating the membrane sheet lining the cavity.
 8. The invention according to claim 7, i. wherein the vertical beams extend to and are attached at their ends to the roof structure.
 9. The invention according to claim 3, j. wherein the inner face of said ring-beam 6 is of a greater diameter than the cavity 1 k. and is supported above the ground level by said support structure 3, 4 l. and said impervious sheet comprises a substantially horizontal annular portion 19 extending radially outward from the mouth of the cavity, m. and a substantially vertical cylindrical portion 21 extending from the outer periphery of said annular portion to said ring-beam.
 10. The invention according to claim 9 n. wherein the support structure comprises a box section 5 supported above the ground surface on the upper ends of freeze pipes which extend upwardly from the ground and are spaced around the mouth of the cavity. 